While the hair, skin, and nails show outward signs of aging, the heart and other internal organs are also (i) ________ by the aging process. Usually there is restricted blood flow to the heart as people age. Part of the reason is that there is a normal atrophy of the heart muscle and the heart valves begin calcifying.
Additionally, the arteries (ii) ________ the blood passes may become less elastiC. Because of some or all of these factors, the reduced flow of blood results in a reduced stamina for people (iii) ________ there is less oxygen passing through and being exchanged in a person’s system. As people age normally, there is also a reduced efficiency of the respiratory system. People have less ability to (iv) ________ deeply and the airway passages become less elastic as a result. Smoking and pollution do not help the respiratory changes in older adults, nor docs the loss of muscle tone and strength. Physical exercise, however, seems to be one of the best ways to (v) ________ improve some cases, slop the changes breathing and muscle tone that develop as people age.
(iv)______
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